Power generation apparatus, control apparatus, and control program

ABSTRACT

A power generation apparatus of the present disclosure includes a power generation unit equipped with a fuel cell, an oxygen-containing gas supply unit configured to supply an oxygen-containing gas to the power generation unit, and a controller configured to control power generation by the power generation unit. The controller reduces power generation by the power generation unit when an operation status of the oxygen-containing gas supply unit satisfies a first predetermined condition and, simultaneously, temperature associated with the power generation apparatus satisfies a second predetermined condition.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Japanese PatentApplication No. 2017-128056 filed on Jun. 29, 2017, the entire contentsof which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a power generation apparatus, acontrol apparatus, and a control program. More specifically, the presentdisclosure relates to a power generation apparatus equipped with a fuelcell, a control apparatus for the power generation apparatus, and acontrol program to be executed by the apparatus.

BACKGROUND

Research and development for various power generation systems which areequipped with a fuel cell such as, for example, a solid oxide fuel cell(hereinafter, referred to as SOFC) is progressing. In relation to apower generation apparatus equipped with a cell stack of fuel cells, anapparatus (hereinafter, referred to as “auxiliary apparatus”) configuredto assist operation of a module that includes the cell stack may be usedin addition to the cell stack. The auxiliary apparatus can operate onelectric power generated by the cell stack or externally suppliedelectric power. The electric power consumption necessary for operationof the auxiliary apparatus can become relatively large, depending on theconfiguration and/or operation status of the power generation apparatus.

CITATION LIST Patent Literature

PTL 1: JP-A-2014-32820

SUMMARY

A power generation apparatus according to an embodiment includes:

a power generation unit equipped with a fuel cell;

an oxygen-containing gas supply unit configured to supply anoxygen-containing gas to the power generation unit; and

a controller configured to control power generation by the powergeneration unit,

wherein the controller reduces power generation by the power generationunit when an operation status of the oxygen-containing gas supply unitsatisfies a first predetermined condition and a temperature associatedwith the power generation apparatus satisfies a second predeterminedcondition.

A control apparats according to an embodiment for controlling a powergeneration apparatus that includes:

a power generation unit equipped with a fuel cell;

an oxygen-containing gas supply unit configured to supply anoxygen-containing gas to the power generation unit; and

a controller configured to control power generation by the powergeneration unit,

wherein the control apparatus reduces power generation by the powergeneration unit when an operation status of the oxygen-containing gassupply unit satisfies a first predetermined condition and a temperatureassociated with the power generation apparatus satisfies a secondpredetermined condition.

A control program according to an embodiment to be performed by acontrol apparatus of a power generation apparatus that includes:

a power generation unit equipped with a fuel cell;

an oxygen-containing gas supply unit configured to supply anoxygen-containing gas to the power generation unit; and

a controller configured to control power generation by the powergeneration unit,

wherein the control program causes the control apparatus to perform astep of reducing power generation by the power generation unit when anoperation status of the oxygen-containing gas supply unit satisfies afirst predetermined condition and a temperature associated with thepower generation apparatus satisfies a second predetermined condition.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a functional block diagram schematically illustrating aconfiguration of a power generation apparatus according to a firstembodiment;

FIG. 2 is a functional block diagram illustrating a portion of the powergeneration apparatus according to the first embodiment in detail;

FIG. 3 is a functional block diagram illustrating another portion of thepower generation apparatus according to the first embodiment in detail;

FIG. 4 is a flowchart illustrating operation of the power generationapparatus according to the first embodiment;

FIG. 5 is a flowchart illustrating another operation of the powergeneration apparatus according to the first embodiment;

FIG. 6 is a flowchart illustrating operation of a power generationapparatus according to a second embodiment;

FIG. 7 is a flowchart illustrating another operation of the powergeneration apparatus according to the second embodiment; and

FIG. 8 is a functional block diagram schematically illustrating anexample variation of the configuration of the power generation apparatusaccording to the first embodiment.

DETAILED DESCRIPTION

An operation mode according to which power consumption by an auxiliaryapparatus is covered by externally supplied electric power and controlis performed to maintain the temperature of a fuel cell is proposed. Insuch an operation mode, electric power generated by the fuel cell issmaller than power consumption by the auxiliary apparatus. It would beadvantageous to reduce power consumption by the auxiliary apparatus in apower generation apparatus equipped with the fuel cell. The presentdisclosure provides a power generation apparatus, a control apparatus,and a control program that reduce power consumption by an auxiliaryapparatus. According to an embodiment, a power generation apparatus, acontrol apparatus, and a control program that reduce power consumptionby an auxiliary apparatus can be provided. Hereinafter, embodiments ofthe present disclosure will be described with reference to theaccompanying drawings. First, a configuration of the power generationapparatus according to an embodiment of the present disclosure will bedescribed.

First Embodiment

FIG. 1 is a functional block diagram schematically illustrating aconfiguration of a power generation apparatus according to a firstembodiment of the present disclosure. FIG. 2 is a functional blockdiagram illustrating a portion of the power generation apparatusaccording to the first embodiment in detail.

The power generation apparatus (the power generation unit) 1 accordingto the first embodiment of the present disclosure is connected to a hotwater storage tank 60, a load 100, and a commercial power source (agrid) 200, as illustrated in FIG. 1. The power generation apparatus 1generates electric power by receiving an externally supplied gas and anoxygen-containing gas (air, etc.) and supplies generated electric powerto the load 100 and the like, as illustrated in FIG. 1.

As illustrated in FIG. 1, the power generation apparatus 1 includes acontroller 10, a memory 12, a fuel cell module 20, a gas supply unit 32,an oxygen-containing gas supply unit 34 (hereinafter, referred to as airsupply unit 34), a reform water supply unit 36, an inverter 40, anexhaust heat recovery unit 50, a circulation water treatment unit 52,and a temperature sensor 80.

As will be described in further detail below, the power generationapparatus 1 includes at least one processor configured as the controller10, in order to provide control and processing capabilities forperforming various functions. According to various embodiments, the atleast one processor may be configured as a single integrated circuit(IC) or a plurality of integrated circuits IC and/or discrete circuitsthat are communicably coupled to one another. The at least one processormay be realized according to various known technologies.

In some embodiments, the processor includes one or more circuits orunits configured to perform one or more data computing procedures oroperations. For example, the processor may be configured as one or moreprocessors, controllers, microprocessors, microcontrollers, applicationspecific integrated circuits (ASIC), digital signal processors,programmable logic devices, field programmable gate arrays, anycombination these devices or their configurations, combinations withother known devices, or their configurations, and perform functionsdescribed below.

The controller 10 is connected to the memory 12, the fuel cell module20, the gas supply unit 32, the air supply unit 34, the reform watersupply unit 36, the inverter 40, and the temperature sensor 80 andcontrols and manages the entire power generation apparatus 1 includingthe functional units mentioned above. The controller 10 acquires andexecutes a program stored in the memory 12 and thus realizes variousfunctions of the functional units of the power generation apparatus 1.When the controller 10 transmits a control signal or various informationto another functional unit, the controller 10 and the other functionalunit simply need to be connected to each other in a wired or wirelessmanner. The control performed by the controller 10 characteristic to thepresent embodiment will be further described below. According to thepresent embodiment, the controller 10 can measure (count) apredetermined time period, such as an operation period (e.g., a powergeneration period) for a cell stack included in the fuel cell module 20.

The controller 10 is connected to the temperature sensor 80, asillustrated in FIG. 1. The temperature sensor 80 is communicativelyconnected with the controller 10 in a wired or wireless manner. Thetemperature sensor 80 measures temperature of a predetermined portion ofthe power generation apparatus 1. Here, the predetermined portion of thepower generation apparatus 1 whose temperature is measured by thetemperature sensor 80 may be various portions including a portion thatenables measurement of temperature of a system of the power generationapparatus 1, depending on a configuration or specification of the powergeneration apparatus 1. In particular, the predetermined portion may be,for example, a portion of the power generation apparatus 1 which iseasily affected by heat in accordance with an operation status when acell stack 24 generates electric power. Alternatively, the predeterminedportion be a portion which easily generates heat in the event of anabnormality or a defect occurring in the power generation apparatus 1.Hereinafter, the temperature of the system of the power generationapparatus 1 measured by the temperature sensor 80, that is thetemperature of the predetermined portion of the power generationapparatus 1, will be referred to as the system temperature, asappropriate.

The temperature sensor 80 may be configured as, for example, athermocouple or the like. However, the temperature sensor 80 is notlimited to the thermocouple and may be configured as any member that canmeasure temperature. For example, the temperature sensor 80 may beconfigured as a thermistor or a platinum resistance thermometer. Thetemperature sensor 80 is communicatively connected with the controller10 in a wired or wireless manner. The temperature sensor 80 transmits asignal based on detected temperature to the controller 10. By receivingthe signal, the controller 10 can grasp the system temperature.

The memory 12 stores information acquired from the controller 10.According to the present embodiment, the memory 12 stores variousthresholds or the like which are used as references when the powergeneration apparatus 1 operates. The memory 12 also stores a program tobe performed by the controller 10. The memory 12 further stores variousdata such as results of computation performed by the controller 10. Thememory 12 can function as a working memory or the like when thecontroller 10 operates, and will be described as such below. The memory12 may be configured as, but is not limited to, a semiconductor memoryor a magnetic disk. For example, the memory 12 may be configured as anoptical storage device such as an optical disk, or a magneto-opticaldisk.

The fuel cell module 20 illustrated in FIG. 1 includes reformers 22 andcell stacks 24, as illustrated in detail in FIG. 2. FIG. 2 illustratesthe controller 10, the fuel cell module 20, and the air supply unit 34of the power generation apparatus 1 illustrated in FIG. 1 and omitsother functional units thereof. According to the present embodiment, thefuel cell module 20 includes two reformers 22A and 22B and two cellstacks 24A and 24B, as illustrated in FIG. 2. Hereinafter, when thereformers 22A and 22B do not need to be distinguished from each other,the reformers 22A and 22B will be collectively referred to as reformers22. Similarly, when the cell stacks 24A and 24B do not need to bedistinguished from each other, the cell stacks 24A and 24B will becollectively referred to as cell stacks 24.

The cell stacks 24 of the fuel cell module 20 generate electric powerusing a gas (a fuel gas) supplied from the gas supply unit 32, andoutput the generated electric power to the inverter 40. The fuel cellmodule 20 is also referred to as a hot module. In the fuel cell module20, the cell stacks 24 generate heat together with the combustion whichoccurs in the power generation. According to the present disclosure, thecell stacks 24 that include the fuel cells for actual power generationwill be referred to as a “power generation unit”, as appropriate.According to the present disclosure, the term “power generation unit”may refer to various functional units that generate electric power. Forexample, “power generation unit” may refer to, in addition to the cellstacks, a single cell or a fuel cell module. According to the presentembodiment, the cell stack 24A will be referred to as a first powergeneration unit, and the cell stack 24B will be referred to as a secondpower generation unit. That is, the power generation apparatus 1according to the present embodiment includes the first power generationunit equipped with fuel cells (the cell stack 24A) and a second powergeneration unit equipped with fuel cells (the cell stack 24B).

The reformers 22 produce hydrogen and/or carbon monoxide using a gassupplied from the gas supply unit 32 and reform water supplied from thereform water supply unit 36. The cell stacks 24 generate electric powerby causing reaction between hydrogen and/or carbon monoxide produced bythe reformers 22 and oxygen in the air. According to the presentembodiment, that is, the cell stacks 24 of the fuel cell generateelectric power through electrochemical reaction. Note that the reformeris configured to perform steam reforming, by way of example. However,the reformer may be of other types such as a reformer configured toperform partial oxidation (PDX) to produce hydrogen using air containingoxygen.

Each of the reformer 22A and the reformer 22B receives a fuel gas fromthe gas supply unit 32, as illustrated in FIG. 2. The reformer 22A isconnected to the cell stack 24A, and the reformer 22B is connected tothe cell stack 24B, as illustrated in FIG. 2. Thus, the reformer 22A andreformer 22B can supply hydrogen and/or carbon monoxide to the cellstack 24A and the cell stack 24B, respectively. In the presentembodiment, as described above, the reformer 22A reforms the gas to besupplied to the cell stack 24A. According to the present embodiment,further, the reformer 22B reforms the gas to be supplied to the cellstack 24B.

Hereinafter, the cell stacks 24 will be described as being a SOFC (solidoxide fuel cell). However, the cell stacks 24 according to the presentembodiment are not limited to SOFC. The cell stacks 24 according to thepresent embodiment may be configured as a fuel cell such as, forexample, a polymer electrolyte fuel cell (PEFC), a phosphoric acid fuelcell (PAFC), a molten carbonate fuel cell (MCFC), or the like. When thecell stacks 24 are of a type different from a SOFC, such as a PEFC orthe like, the cell stacks 24 do not need to be accommodated in the samehousing as the reformers, and also do not need to include a fuel cellmodule as described above. When the cell stacks 24 are of a typedifferent from a SOFC such as PEFC or the like, the cell stacks 24 maybe accommodated in the same housing as the reformers or do not need tobe located in the vicinity of the reformers. The power generationapparatus 1 according to the present embodiment includes two cell stacks24A and 24B, as illustrated in FIG. 2. In other embodiments, however,the cell stacks 24 may be configured as, for example, four cell stackseach of which can generate electric power of approximately 700 W. Inthis case, the fuel cell module 20 can output electric power ofapproximately 3 kW as a whole. In other embodiments, the cell stacks 24may be configured as, for example, one cell stack.

The fuel cell module 20 and the cell stacks 24 according to the presentembodiment are not limited to the configurations described above and mayhave various configurations. In the present embodiment, the powergeneration apparatus 1 simply needs to include two or more powergeneration units configured to generate electric power utilizing a gas.Further, for example, the power generation apparatus 1 may include onefuel cell in place of the cell stacks 24 as the power generation unit.Further, the power generation unit according to the present embodimentmay be configured as, for example, a fuel cell that does not include amodule, such as PEFC.

The power generation apparatus 1 includes a gas supply unit 32, an airsupply unit 34, and a reform water supply unit 36, as illustrated inFIG. 1. The gas supply unit 32 supplies a gas to the reformers 22 in thefuel cell module 20. The air supply unit 34 supplies air to the cellstacks 24 in the fuel cell module 20. The reform water supply unit 36supplies water to be reformed to the reformers 22 in the fuel cellmodule 20.

The gas supply unit 32 illustrated in FIG. 1 supplies a gas to the cellstacks 24 via the reformers 22 in the fuel cell module 20. At this time,the gas supply unit 32 controls a flow rate of the gas to be supplied tothe cell stacks 24, based on the control signal from the controller 10.In the present embodiment, the gas supply unit 32 may be configured as,for example, a gas line. The gas supply unit 32 may perform adesulfurization treatment on the gas or preliminarily heat the gas. As aheat source for heating the gas, exhaust heat from the cell stacks 24may be utilized. The gas is, for example, a city gas, LPG, or the like,but not limited thereto. For example, the gas may be a natural gas or acoal gas, depending on the fuel cell. In the present embodiment, the gassupply unit 32 supplies the fuel gas to be used for the electrochemicalreaction when the cell stacks 24 generate electric power.

The gas supplied to the fuel cell module 20 from the gas supply unit 32travels through two pathways and is supplied to each of the cell stack24A and the cell stack 24B, as illustrated in FIG. 2. Further, the gashaving passed through the reformer 22A is supplied to the cell stack24A, and the gas having passed through the reformer 22B is supplied tothe cell stack 24B, as illustrated in FIG. 2. In the present embodiment,as described above, the pathway of the gas supplied by the gas supplyunit 32 includes a first gas line and a second gas line. In the presentembodiment, the first gas line supplies a gas to the cell stack 24A, andthe second gas line supplies a gas to the cell stack 24B. In the presentembodiment, the gas supply unit 32 supplies a fuel gas to the powergeneration unit 24. Here, the gas supply unit 32 may receive a gassupplied from one gas supply source via two pathways. Alternatively, thegas supply unit 32 may receive a gas from each of different gas supplysources.

The gas supply unit 32 is communicably connected with the controller 10in a wired or wireless manner, as illustrated in FIG. 1. The gas supplyunit 32 includes a gas pump and a flowmeter. Here, the gas pump sendsgas to the fuel cell module 20 from the gas supply unit 32. Theflowmeter measures the flow rate of the gas sent from the gas supplyunit 32. Information regarding the flow rate measured by the flowmeteris transmitted to the controller 10. Thus, the controller 10 can graspthe flow rate of the gas measured by the flowmeter. Further, because thecontroller 10 is communicably connected to the gas supply unit 32, thecontroller 10 can control (increase or reduce) the flow rate of the gasto be sent to the reformers 22A and 22B by the gas pump. In the presentembodiment, accordingly, the controller 10 can adjust the flow rate ofeach of the gas to be supplied to the cell stack 24A and the gas to besupplied to the cell stack 24B.

The air supply unit 34 illustrated in FIG. 1 supplies air to the cellstacks 24 in the fuel cell module 20. At this time, the air supply unit34 controls the flow rate of air to be supplied to the cell stacks 24,based on a control signal from the controller 10. In the presentembodiment, the air supply unit 34 may be configured as, for example, anair line. The air supply unit 34 may preliminarily heat externallyobtained air and supply the heated air to the cell stacks 24. As a heatsource for heating the air, exhaust heat from the cell stacks 24 may beutilized. In the present embodiment, the air supply unit 34 supplies airto be used for the electrochemical reaction when the cell stacks 24generate electric power. In the present embodiment, air supplied by theair supply unit 23 does not necessarily need to include all componentsof air, such as nitrogen, oxygen, carbon dioxide, and argon. Forexample, air supplied by the air supply unit 34 may contain oxygen aloneor in combination of oxygen and another gas.

According to the present embodiment, the air supply unit 34 includes twoair blowers 96A (a first air supply unit) and 96B (a second air supplyunit) and two flowmeters 98A and 98B, as illustrated in FIG. 2.Hereinafter, when the air blowers 96A and 96B are not discriminated fromeach other, the air blowers 96A and 96B will be collectively referred toas air blowers 96. Similarly, when the flowmeters 98A and 98B are notdiscriminated from each other, the flowmeters 98A and 98B will becollectively referred to as flowmeters 98.

According to the present embodiment, air supplied to the air supply unit34 is supplied to the air blower 96A and the air blower 96B via the twopathways from one supply source, as illustrated in FIG. 2. The airblower 96A is connected to the flowmeter 98A, and the air blower 96B isconnected to the flowmeter 98B, as illustrated in FIG. 2. Thus, the airblower 96A can supply air to the cell stack 24A via the flowmeter 98A,and the air blower 96B can supply air to the cell stack 24B via theflowmeter 98B. In the example illustrated in FIG. 2, air is supplied tothe air blower 96A and the air blower 96B via the two pathways from onesupply source. However, for example, the air blowers 96A and 96B mayreceive air from the respective supply sources.

The air blower 96A blows air supplied to the air supply unit 34 to thecell stack 24A of the fuel cell module 20 via the flowmeter 98A, and theair blower 96B blows air supplied to the air supply unit 34 to the cellstack 24B via the flowmeter 98B. The air blowers 96A and 96B may beconfigured as any appropriate member such as, for example, a fan capableof blowing air to the cell stacks 24A and 24B.

The flowmeters 98A and 98B measure the respective flow rates of airflowing therethrough. Here, the flow rates of air measured by theflowmeters 98A and 98B may be, for example, an amount of air that movesthrough the flowmeter 98A per unit time and an amount of air that movesthrough the flowmeter 98B per unit time. The flowmeters 98A and 98B maybe configured as any appropriate members capable of measuring the flowrate of air.

The air supply unit 34 is communicably connected with the controller 10in a wired or wireless manner, as illustrated in FIG. 2. Informationregarding the flow rate of air measured by each of the flowmeter 98A andthe flowmeter 98B is transmitted to the controller 10. Thus, thecontroller 10 can grasp the flow rate of air measured by each of theflowmeter 98A and the flowmeter 98B. Also, because the controller 10 iscommunicably connected with the air supply unit 34, the controller 10can adjust (increase or reduce) the flow rate of air blown by the airblowers 96A and 96B to the cell stacks 24A and 24B, respectively.According to the present embodiment, thus, the controller 10 can adjustthe flow rate of air to be supplied to the cell stack 24A and the flowrate of air to be supplied to the cell stack 24B.

The air supply unit 34 according to the present embodiment includes acurrent sensor 70A and a current sensor 70B, as illustrated in FIG. 2.The current sensor 70A detects a current supplied to the air blower 96A.Similarly, the current sensor 70B detects a current supplied to the airblower 96B. Hereinafter, when the current sensors 70A and 70B are notdiscriminated from each other, the current sensors 70A and 70B will becollectively referred to as current sensors 70.

The current sensor 70 may be configured as, for example, CT (CurrentTransformer). However, the current sensor 70 is not limited to a CT andmay be configured as any appropriate component capable of measuring acurrent. For example, the current sensor 70 may be c based on aprinciple such as the Hall element method, the Rogowski method, or thezero flux method. The current sensor 70 is communicatively connectedwith the controller 10 in a wired or wireless manner. The current sensor70 transmits a signal based on a detected current to the controller 10.By receiving the signal, the controller 10 can grasp an operation statusof the air blower 96. In the present embodiment, it is necessary tosimply grasp the operation status of the air blower 96. Thus, a voltagesensor or the like may be used in place of the current sensor 70, inorder to grasp the operation status.

According to the present embodiment, the controller 10 determines theoperation status of the air blower 96, based on the current supplied tothe air blower 96. For example, by preliminarily understanding acorrespondence between the current supplied to the air blower 96 and itsoperation status in advance, the controller 10 can determine theoperation status, based on the current supplied to the air blower 96.For example, when a current supplied to the air blower 96 is zero, thecontroller 10 may determine that the air blower 96 is stopped. When acurrent at a predetermined small value is supplied to the air blower 96,the controller 10 may determine that the air blower 96 is slightlyoperating. When a current close to a maximum value that can be suppliedto the air blower 96 is supplied to the air blower 96, the controller 10may determine that the air blower 96 is in an operation status withapproximately full power. As described above, the controller 10 candetermine particular operation statuses of the air blower 96corresponding to particular values of a current supplied to the airblower 96. According to the present embodiment, it is necessary tosimply determine the operation status of the air blower 96. Thus, thecontroller 10 may determine the operation status of the air blower 96 inan indirect manner, based on, for example, a flow rate of air passingthrough the flowmeter 98, rather than power consumption by the airblower 96. Alternatively, the controller 10 may determine the operationstatus of the air blower 96 by comparing the flow rate of the air withthe value of the current.

In the power generation apparatus 1 according to the present embodiment,the air supply unit 34 is not limited to the configuration asillustrated in FIG. 2. For example, although in the air supply unit 34illustrated in FIG. 2 the flowmeter 98 measures the flow rate of airsent by the air blower 96, the flowmeter 98 may measure a flow rate ofair to be blown by the air blower 96.

Further, in the air supply unit 34 illustrated in FIG. 2, the air blower96A supplies air to the cell stack 24A, and the air blower 96B suppliesair to the cell stack 24B. This configuration enables separate controlof the cell stacks 24A and 24B to supply air at different flow rates.Alternatively, in a more simplified configuration, air blown by the airblowers 96A and 96B may be collected into one supply line and thensupplied to the fuel cell module 20. Air supplied from one supply linemay be supplied to the cell stack 24A and the cell stack 24B in the fuelcell module 20. In this case, the flow rates of air supplied to the cellstack 24A and air supplied to the cell stack 24B are approximately thesame. In a further simplified configuration, the air supply unit 34 mayinclude each one of the air blower 96 and the flowmeter 98. In thiscase, the air supply unit 34 may supply air to the fuel cell module 20via one supply line. This configuration may be employed when, forexample, the fuel cell module 20 includes one cell stack 24.

The reform water supply unit 36 illustrated in FIG. 1 generates steamand supplies the generated steam to the reformers 22 of the fuel cellmodule 20. At this time, the reform water supply unit 36 controls a flowrate of steam to be supplied to the cell stacks 24, based on a controlsignal from the controller 10. According to the present embodiment, thereform water supply unit 36 may be configured as, for example, a waterreform line. The reform water supply unit 36 may generate steam usingwater recovered from the exhaust from the cell stacks 24 as a rawmaterial. As a heat source for generating steam, exhaust heat from thecell stacks 24 may be utilized.

The inverter 40 is electrically connected to the cell stacks 24 in thefuel cell module 20. The inverter 40 converts DC power generated by thecell stacks 24 into AC power using an AC-DC converter. The inverter 40may include a DC-DC converter in addition to the AC-DC converter. DCpower output from the inverter 40 is supplied to the load 100 via adistribution board or the like. The load 100 receives electric poweroutput from the inverter 40 via the distribution board or the like.Although the load 100 is configured as one member in FIG. 1, the load100 may be configured as any number of various electric apparatusesconstituting the load. The load 100 can receive electric power from thecommercial power supply 200 via the distribution board or the like. Asillustrated in FIG. 1, the inverter 40 and the controller 10 may becommunicatively coupled with each other in a wired or wireless manner.This connection enables the controller 10 to control output of AC powerby the inverter 40.

The exhaust heat recovery unit 50 recovers exhaust heat from the exhaustarising from power generation by the cell stacks 24. The exhaust heatrecovery unit 50 may be configured as, for example, a heat exchanger orthe like. The heat exchanger performs heat exchange on heat caused bypower generation by the cell stacks 24 using a heat medium. According tothe present embodiment, as described above, the heat exchanger (the heatexchange unit) performs heat exchange of heat caused by power generationby the cell stacks 24 (the power generation unit) using the heat medium(circulation water). The exhaust heat recovery unit 50 is connected tothe circulation water treatment unit 52 and the hot water storage tank60.

The circulation water treatment unit 52 circulates water from the hotwater storage tank 60 to the exhaust heat recovery unit 50. Hereinafter,water (i.e., the heat medium) circulating from the hot water storagetank 60 to the exhaust heat recovery unit 50 will be referred to ascirculation water, as appropriate. The circulation water treatment unit52 includes a circulation pump for circulating the circulation water.The circulation water supplied to the exhaust heat recovery unit 50 bythe circulation water treatment unit 52 is heated by heat recovered bythe exhaust heat recovery unit 50 and then returns to the hot waterstorage tank 60. The exhaust heat recovery unit 50 discharges exhaustfrom which heat is recovered to the outside of the power generationapparatus 1. Heat recovered by the exhaust heat recovery unit 50 may beused to heat gas, air, or reformed water, as described above.

The hot water storage tank 60 is connected to the exhaust heat recoveryunit 50 and the circulation water treatment unit 52. The hot waterstorage tank 60 can store hot water produced by utilizing exhaust heatrecovered from the cell stacks 24 of the fuel cell module 20.

The temperature sensor 80 described above can measure temperature of apredetermined portion of the power generation apparatus 1. The powergeneration apparatus 1 according to the present embodiment performscontrol based on system temperature detected by the temperature sensor80 and temperature measured at other portions. According to the presentembodiment, as described above, the heat exchanger constituting at leasta portion of the exhaust heat recovery unit 50 performs heat exchange ofheat caused by power generation by the cell stacks 24 using the heatmedium such as the circulation water. In the present embodiment, aresult of measurement of temperature of the circulation water isreflected on the control performed by the power generation apparatus 1.

FIG. 3 is a diagram illustrating the portion of the power generationapparatus 1 illustrated in FIG. 1 in detail. Out of functional units ofthe power generation apparatus 1 illustrated in FIG. 1, the fuel cellmodule 20, the exhaust heat recovery unit 50, and the circulation watertreatment unit 52 are illustrated in FIG. 3, and other functional unitsare omitted. FIG. 3 also illustrates the hot water storage tank 60connected to the power generation apparatus 1.

As described above, in the power generation apparatus 1, the heatexchanger constituting at least a portion of the exhaust heat recoveryunit 50 performs heat exchange using the heat medium such as thecirculation water. Also, the circulation pump constituting at least aportion of the circulation water treatment unit 52 circulates thecirculation water. Accordingly, the pathway between the exhaust heatrecovery unit 50 and the circulation water treatment unit 52 and theconnection between the exhaust heat recovery unit 50 and the hot waterstorage tank 60 form a pathway for circulating the heat medium such asthe circulation water. In the present embodiment, temperature of thecirculation water circulating in the pathway is measured.

The exhaust heat recovery unit 50 includes a temperature sensor 84, asillustrated in FIG. 3. The temperature sensor 84 measures temperatureassociated with the heat exchanger constituting the exhaust heatrecovery unit 50. For example, the temperature sensor 84 may measureinternal temperature of the heat exchanger constituting the exhaust heatrecovery unit 50, as illustrated in FIG. 3. Further, for example, thetemperature sensor 84 may be disposed at a location within the heatexchange where the temperature sensor 84 can measure temperature of thecirculation water after the heat exchanger performs heat exchange ofheat caused by power generation by the cell stacks 24. The temperaturesensor 84 may be disposed at various locations that allow accuratemeasurement of temperature of the circulation water, depending on acharacteristic or specification of each unit constituting the powergeneration apparatus 1. Hereinafter, temperature measured by thetemperature sensor 84, that is the internal temperature of the heatexchanger constituting the exhaust heat recovery unit 50, will bereferred to as the “internal temperature”, as appropriate.

Further, the pathway of the circulation water that connects thecirculation water treatment unit 52 and the hot water storage tank 60together is provided with a temperature sensor 86 and a temperaturesensor 88, as illustrated in FIG. 3.

The temperature sensor 86 measures the temperature associated with thecirculation water (the heat medium). For example, the temperature sensor86 may measure the temperature of a predetermined portion of the pathwayfor circulating the circulation water. In particular, the temperaturesensor 86 may measure the temperature of the circulation waterdischarged from an outlet of the heat exchanger after the heat exchangerconstituting the exhaust heat recovery unit 50 performs heat exchangeusing heat from the fuel cell module 20. The temperature sensor 86 maymeasure the temperature of the circulation water discharged from anoutlet of the exhaust heat recovery unit 50 after the heat exchangerconstituting the exhaust heat recovery unit 50 performs heat exchange,as illustrated in FIG. 3. The temperature sensor 86 may be locatedexternal to the heat exchanger. Hereinafter, the temperature measured bythe temperature sensor 86, i.e., the temperature of the circulationwater discharged from the heat exchanger or the exhaust heat recoveryunit 50 will be referred to as the “first outlet temperature”, asappropriate.

The temperature sensor 88 measures the temperature associated with thecirculation water (the heat medium), in a manner similar to thetemperature sensor 86. The temperature sensor 86 and the temperaturesensor 88 may be arranged being relatively spaced apart from each other.This arrangement enables, for example, detection of leakage of thecirculation water from the pathway when there is a relatively largedifference between the temperature measured by the temperature sensor 86and the temperature measured by the temperature sensor 88. For example,the temperature sensor 88 may measure a portion different from a portionmeasured by the temperature sensor 86, as the temperature of apredetermined portion in the pathway of the circulation water. Inparticular, after the circulation water is discharged from the exhaustheat recovery unit 50, the temperature sensor 88 may measure thetemperature of the circulation water discharged from the outlet of thepower generation apparatus 1. Hereinafter, the temperature measured bythe temperature sensor 88, i.e., the temperature of the circulationwater at the outlet of the power generation apparatus 1 will be referredto as the “second outlet temperature”, as appropriate. The temperaturesensor 88 may be disposed before an inlet of the circulation water lineto the hot water storage tank 60 within the power generation apparatus1.

The temperature sensors 84, 86 and 88 may be configured as, for example,thermocouples or the like. However, the temperature sensor 84, 86 and 88are not limited to the thermocouples, in a manner similar to thetemperature sensor 80, and may be configured as any member capable ofmeasuring temperature of a heat medium such as the circulation water.Each of the temperature sensors 84, 86 and 88 is communicativelyconnected with the controller 10 in a wired or wireless manner. Each ofthe temperature sensors 84, 86 and 88 transmits a signal based on thedetected temperature to the controller 10. By receiving the signals, thecontroller 10 can acquires the internal temperature, the first outlettemperature, and the second outlet temperature.

Next, an operation of the power generation apparatus 1 according to thepresent embodiment will be described.

The power generation apparatus 1 according to the present embodiment canperform control to inhibit boiling in the exhaust heat recovery unit 50or the like, by circulating the circulation water during normaloperation. According to the present embodiment, during such control toinhibit boiling, the auxiliary apparatus is inhibited from consumingexcessive power. The term “auxiliary apparatus” used herein may refer toan apparatus that supports the operation of the fuel cell module 20. Inparticular, the “auxiliary apparatus” may refer to the air supply unit34 that includes the air blower 96, and the circulation water treatmentunit 52 that includes the circulation pump, in the present embodiment.However, the “auxiliary apparatus” used in the present embodiment is notlimited to these functional units and may include other functional unitsor may be partially substituted by another functional unit, asappropriate.

FIG. 4 is a flow chart illustrating the operation of the powergeneration apparatus 1 according to the first embodiment.

At the initiation of the operation illustrated in FIG. 4, it is assumedthat the power generation apparatus 1 has already started and the cellstacks 24 are generating electric power. When the operation illustratedin FIG. 4 starts, the controller 10 determines whether the operationstatus of the air supply unit 34 satisfies a first predeterminedcondition (step S11).

As described above, the controller 10 can determine the operation statusbased on the current supplied to the air blower 96. In the presentembodiment, in order to determine whether the first predeterminedcondition is satisfied, a threshold of a current to be detected by acurrent sensor 70 is set. Based on the threshold, the controller 10determines the operation status of the air blower 96 constituting theair supply unit 34. Hereinafter, in order to determine whether the airblower 96 is reliably operating, the first predetermined condition isdetermined to be that the current detected by the current sensor 70 isequal to or higher than a threshold of, for example, 1.7 A. Inparticular, the first predetermined condition may be determined to bethat a sum of the currents detected by the current sensors 70A and 70Bis equal to or higher than the threshold of 1.7 A. Here, this thresholdis merely illustrative and may be appropriately set based on theconfiguration or specification of each functional unit. Also, forexample, in order to determine that the air blower 96 is operating withapproximately full force, a threshold of the current to be detected bythe current sensor 70 may be set. When the first predetermined conditionis satisfied, the controller 10 determines that the air supply unit 34is reliably operating in the power generation apparatus 1. In this case,it may be determined that the circulation water treatment unit 52 iscontrolled so as to inhibit boiling in the exhaust heat recovery unit 50or the like.

When the controller 10 determines in step S11 that the operation statusof the air supply unit 34 does not satisfy the first predeterminedcondition, the controller 10 returns to step S11 until the firstpredetermined condition is satisfied. On the other hand, when thecontroller 10 determines in step S11 that the operation status of theair supply unit 34 satisfies the first predetermined condition, thecontroller 10 proceeds to step S12.

In step S12, the controller 10 determines whether the temperatureassociated with the power generation apparatus 1 satisfies a secondpredetermined condition. In step 12, in particular, the controller 10determines that the second predetermined condition is satisfied whentemperature of a predetermined portion associated with the auxiliaryapparatus of the power generation apparatus 1 is relatively high.

For example, the controller 10 determines that the second predeterminedcondition is satisfied when any of the following (1) to (3) issatisfied.

(1) The internal temperature (of the heat exchanger) measured by thetemperature sensor 84 is 100° C. or higher.

(2) The first outlet temperature (of the circulation water) measured bythe temperature sensor 86 is 80° C. or higher.

(3) The second outlet temperature (of the circulation water) measured bythe temperature sensor 88 is 80° C. or higher.

Here, each of the values of the temperature are merely illustrative andmay be appropriately set based on the configuration or specification ofeach functional unit.

When the controller 10 determines in step S12 that the temperatureassociated with the power generation apparatus 1 does not satisfy thesecond predetermined condition, the controller 10 returns to step S11and performs the operation of step S11. On the other hand, when thecontroller 10 determines in step S12 that temperature associated withthe power generation apparatus 1 satisfies the second predeterminedcondition, the controller 10 proceeds to step S13.

When the first predetermined condition is satisfied in step S11, thecirculation water treatment unit 52 is already controlled to inhibitboiling in the exhaust heat recovery unit 50. When the secondpredetermined condition is satisfied in step S12, the temperature of thepredetermined portion associated with the auxiliary apparatus in thepower generation apparatus 1 is relatively high. In this case,maintaining or boosting the operation of the auxiliary apparatus mayincrease power consumption by the auxiliary apparatus. In the presentembodiment, thus, when the first and second predetermined conditions aresimultaneously satisfied, the controller 10 controls to reduce powergeneration by the power generation apparatus 1 (step S13). In step S13,for example, in a case in which the power generation apparatus 1generates electric power outputting 3 kW, the controller 10 may reducethe output to 2.5 kW. In particular, the controller 10 controls each ofthe cell stacks 24 to reduce the output therefrom. Here, the respectivevalues of the electric power are merely illustrative and may beappropriately set based on the configuration or specification of eachfunctional unit.

The reduction of power generation by the power generation apparatus 1results in a reduction of electric power used for operating the airblower 96 in the air supply unit 34. Further, the reduction of powergeneration by the power generation apparatus 1 also reduces electricpower used for operating the circulation pump in the circulation watertreatment unit 52. Thus, by reducing power generation by the powergeneration apparatus 1 of the present embodiment, power consumption bythe auxiliary apparatus can be reduced.

In FIG. 4, when the operation status of the air supply unit 34 satisfiesthe first predetermined condition in step S11, it is determined in stepS12 whether the temperature associated with the power generationapparatus 1 satisfies the second predetermined condition. However, theorder of steps S11 and S12 may be inverted, or the determination of stepS11 and the determination of step S12 may be performed independently ofeach other.

In the present embodiment, as described above, when the operation statusof the air supply unit 34 satisfies the first predetermined conditionand, simultaneously, the temperature associated with the powergeneration apparatus 1 satisfies the second predetermined condition, thecontroller 10 reduces power generation by the power generation unit (thecell stacks 24). Here, the first predetermined condition may bedetermined to be that power consumption of the air supply unit 34 isequal to or more than a predetermined threshold. For example, the firstpredetermined condition may be determined to be that a current suppliedto the air supply unit 34 is equal to or more than a predeterminedthreshold (e.g., 1.7 A).

The second predetermined condition may be determined to be that thetemperature associated with the heat exchange unit (the heat exchanger)is equal to or higher than a predetermined threshold, or the temperatureassociated with the heat medium (the circulation water) is equal to orhigher than a predetermined threshold. For example, the temperatureassociated with the heat exchange unit may be the internal temperatureof the heat exchanger unit. Further, for example, the temperatureassociated with the heat medium may be temperature of a predeterminedportion of the pathway of the heat medium. The temperature associatedwith the heat medium may be temperature of any one of a plurality ofpredetermined portions (e.g. the internal temperature, the first outlettemperature, and the second outlet temperature) in the pathway forcirculating the circulating heat medium.

Next, an operation for stopping the reduction of power generationillustrated in FIG. 4 will be described.

In FIG. 4, when the temperature of the predetermined portion associatedwith the auxiliary apparatus is relatively high during the control toinhibit boiling in the exhaust heat recovery unit 50, power generationby the power generation apparatus 1 is reduced. However, when thisoperation makes the temperature of the predetermined portion associatedwith the auxiliary apparatus relatively low, there is not muchsignificance in maintaining the operation to reduce power generation bythe power generation apparatus 1. In this case, accordingly, theoperation to reduce power generation by the power generation apparatus 1is stopped.

FIG. 5 is a flow chart illustrating an operation of the power generationapparatus 1 according to the first embodiment.

At the time of initiation of the operation illustrated in FIG. 5, it isassumed that the power generation apparatus 1 has already started theoperation for stopping the reduction of power generation describedreferring to FIG. 4. When the operation illustrated in FIG. 5 starts,the controller 10 determines whether the operation period to reduce thepower generation described referring to FIG. 4 is equal to or longerthan a predetermined period (step S21).

In step S21, the predetermined period may be, for example, 5 minutes.Here, this operation is merely illustrative and may be appropriately setbased on the configuration or specification of each functional unit. Inparticular, the operation may be determined to be a period after whichit should be safe to expect that the temperature of the predeterminedportion associated with the auxiliary apparatus is sufficiently low,following the operation to reduce power generation is performed for theperiod.

When it is determined that the operation to reduce power generation hasnot continued for the predetermined period in step S21, the controller10 returns to step S21 until the operation is continued for thepredetermined period. On the other hand, when it is determined in stepS21 that the operation to reduce power generation has continued for thepredetermined period, the controller 10 proceeds to step S22.

In step S22, the controller 10 determines whether the temperatureassociated with the power generation apparatus 1 satisfies a thirdpredetermined condition (step S22). In step S22, in particular, when thetemperature of a predetermined portion associated with the auxiliaryapparatus in the power generation apparatus 1 is relatively low, thecontroller 10 determines that the third predetermined condition issatisfied.

According to the present embodiment, for example, the controller 10determines that the third predetermined condition is satisfied when anyof the following (1) to (3) is satisfied.

(1) The internal temperature (of the heat exchanger) measured by thetemperature sensor 84 is 95° C. or lower.

(2) The first outlet temperature (of the circulation water) measured bythe temperature sensor 86 is 78° C. or lower.

(3) The second outlet temperature (of the circulation water) measured bythe temperature sensor 88 is 78° C. or lower.

Here, each of the values of the temperature are merely illustrative andmay be appropriately set based on the configuration or specification ofeach functional unit.

When the controller 10 determines in step S22 that the temperatureassociated with the power generation apparatus 1 does not satisfy thethird predetermined condition, the controller 10 returns to step S21 andperforms the operation of step S21. On the other hand, when thecontroller 10 determines in step S22 that the temperature associatedwith the power generation apparatus 1 satisfies the third predeterminedcondition, the controller 10 proceeds to step S23.

In step S23, the controller 10 stops the operation to reduce powergeneration by the power generation apparatus 1. In particular, thecontroller 10 restores the output of the electric power generated by thepower generation apparatus 1 prior to the operation to reduce the powergeneration performed in step S13. For example, when the power generationby the power generation apparatus 1 is reduced to 2.5 kW from 3 kW instep S13, the controller 10 controls such that the power generationapparatus 1 restores the output of 3 kW in step 23 of FIG. 5. Asdescribed above, when the temperature of the predetermined portionassociated with the auxiliary apparatus becomes relatively low, thepower generation apparatus 1 according to the present embodiment cangenerate electric power at an original output level.

In FIG. 5, when the operation to reduce power generation is continuedfor the predetermined period in step S21, whether the temperatureassociated with the power generation apparatus 1 satisfies the thirdpredetermined condition is determined in step S22. However, thedeterminations of steps S21 and step S22 may be inverted or performedindependently of each other.

According to the present embodiment, as described above, the controller10 may stop the reduction of power generation by the power generationunit (the cell stacks 24) when the operation for reducing powergeneration by the power generation unit 24 is maintained for equal to orlonger than the predetermined period and, simultaneously, thetemperature associated with the power generation apparatus 1 satisfiesthe third predetermined condition. Here, the third predeterminedcondition may be determined to be that the temperature associated withthe heat exchanger (the heat exchanging apparatus) is equal to or lowerthan a predetermined threshold and, simultaneously, the temperatureassociated with the heat medium (the circulation water) is equal to orlower than a predetermined threshold. The temperature associated withthe heat exchange unit may be internal temperature of the heat exchangeunit. The temperature associated with the heat medium may be temperatureof a predetermined portion of the pathway for circulating the heatmedium. The temperature associated with the heat medium may betemperature of any one of a plurality of predetermined portions (e.g.the internal temperature, the first outlet temperature, and the secondoutlet temperature) in the pathway for circulating the heat medium.

Second Embodiment

Next, a power generation apparatus according to a second embodiment ofthe present disclosure will be described.

The power generation apparatus of the second embodiment can employ aconfiguration similar to that of the power generation apparatus 1described in the first embodiment. Thus, the configuration of the powergeneration apparatus of the second embodiment similar to that of thepower generation apparatus 1 of the first embodiment will be simplifiedor omitted, as appropriate.

The power generation apparatus according to the second embodiment has aconfiguration in which the controller 10 of the power generationapparatus 1 of the first embodiment performs control in a differentmanner. In the second embodiment, when an increase in power consumptionby the auxiliary apparatus is expected, the controller 10 performscontrol to inhibit excessive power consumption by the auxiliaryapparatus.

FIG. 6 is a flowchart illustrating an operation of the power generationapparatus 1 according to the second embodiment.

At the initiation of the operation illustrated in FIG. 6, it is assumedthat the power generation apparatus 1 has already started and the cellstacks 24 are generating electric power. When the operation illustratedin FIG. 6 starts, the controller 10 determines whether the operationstatus of the air supply unit 34 satisfies the first predeterminedcondition (step S31).

Here, the first predetermined condition in the present embodiment can beset in a manner similar to the first predetermined condition of thefirst embodiment described in step S11 of FIG. 4. That is, in thepresent embodiment also, the first predetermined condition may bedetermined to be that the current detected by the current sensor 70 isequal to or higher than the threshold of, for example, 1.7 A. Inparticular, the first predetermined condition may be determined to bethat the sum of the current values detected by the current sensors 70Aand 70B is equal to or higher than the threshold of 1.7 A. Here, thethreshold is merely illustrative and may be appropriately set based onthe configuration or specification of each functional unit. Because thecontrol performed by the controller 10 in step S31 is similar to thecontrol in step S11 of FIG. 4, a more detailed description thereof willbe omitted.

When the controller 10 determines in step S31 that the operation statusof the air supply unit 34 does not satisfy the first predeterminedcondition, the controller 10 returns to step S11 until the firstpredetermined condition is satisfied. On the other hand, when thecontroller 10 determines in step S31 that the operation status of theair supply unit 34 satisfies the first predetermined condition, thecontroller 10 proceeds to step S32.

In step S32, the controller 10 determines whether the temperatureassociated with the power generation apparatus 1 satisfies a secondpredetermined condition (step S32). In step S32, in particular, when thetemperature of a predetermined portion associated with the auxiliaryapparatus in the power generation apparatus 1 is relatively high, thecontroller 10 determines that the second predetermined condition issatisfied.

In the present embodiment, for example, when the system temperaturemeasured by the temperature sensor 80 is 45° C. or higher, thecontroller 10 determines that the second predetermined condition issatisfied. Here, the temperature is merely illustrative and may beappropriately set based on the configuration or specification of eachfunctional unit.

When the controller 10 determines in step S32 that the temperatureassociated with the power generation apparatus 1 does not satisfy thesecond predetermined condition, the controller 10 returns to step S31and performs the operation of step S31. On the other hand, when thecontroller 10 determines in step S32 that the temperature associatedwith the power generation apparatus 1 satisfies the second predeterminedcondition, the controller 10 proceeds to step S33.

In step S33, the controller 10 determines whether an operation period ofthe power generation apparatus 1 is equal to or longer than thepredetermined period. In step S33, the controller 10 determines whetherthe operation of the power generation apparatus 1 is equal to or longerthan, for example, 60,000 hours. For example, when the operation periodof the power generation apparatus 1 is equal to or longer than 60,000hours, power consumption by the auxiliary apparatus tends to increaseduring power generation by the power generation apparatus 1, for areasons such as degradation of the cell stacks 24. Here, 60,000 hoursmentioned above is merely illustrative and may be appropriately setbased on the configuration or specification of each functional unit.

When the controller 10 determines in step S33 that the operation periodof the power generation apparatus 1 is not equal to or longer than thepredetermined period, the controller 10 may return to step S31 until theoperation period reaches the predetermined period, or end the operationillustrated in FIG. 6. On the other hand, when the controller 10determines in step S33 that the operation period of the power generationapparatus 1 is equal to or longer than the predetermined period, thecontroller 10 proceeds to step S34.

In step S34, the controller 10 controls to reduce power generation bythe power generation apparatus 1 (step S34). In step S34, for example,when the power generation apparatus 1 generates electric power at anoutput of 3 kW, the controller 10 may reduce the output to 2.5 kW. Here,these values of electric power are merely illustrative and may beappropriately set based on the configuration or specification of eachfunctional unit. Because the control by the controller 10 in step S34 issimilar to the control in step S13 of FIG. 4, a more detaileddescription thereof will be omitted.

The reduction of power generation by the power generation apparatus 1results in a reduction of electric power used for operating the airblower 96 in the air supply unit 34. The reduction of power generationby the power generation apparatus 1 also reduces the system temperatureof the power generation apparatus 1, leading the reduction of powerconsumption by the auxiliary apparatus such as electric power used foroperating the circulation pump in the circulation water treatment unit52. Thus, by reducing power generation by the power generation apparatusof the present embodiment, power consumption by the auxiliary apparatuscan be reduced.

In FIG. 6, when the operation status of the air supply unit 34 satisfiesthe first predetermined condition in step S31, whether the temperatureassociated with the power generation apparatus 1 satisfies the secondpredetermined condition is determined in step S32. In FIG. 6, further,when the temperature associated with the power generation apparatus 1satisfies the second predetermined condition in step S32, whether theoperation period of the power generation apparatus 1 is equal to orlonger than the predetermined period is determined in step S33. However,the order of the determinations in steps S31, S32, and S33 may beappropriately changed, and some or all of the determinations in thesesteps may be performed independently of one another.

According to the present embodiment, as described above, when the firstand second predetermined conditions are satisfied and, simultaneously,the operation period of the power generation apparatus 1 is equal to orlonger than the predetermined period, power generation by the powergeneration unit (the cell stacks 24) may be reduced. Here, the firstpredetermined condition may be determined to be that power consumptionby the air supply unit 34 is equal to or more than a predeterminedthreshold. Alternatively, the first predetermined condition may bedetermined to be that the current supplied to the air supply unit 34 isequal to or more than a predetermined threshold (e.g., 1.7 A). Thesecond predetermined condition may be determined to be that temperatureof a predetermined portion of the power generation apparatus 1 is equalto or higher than predetermined temperature (e.g., 45° C.).

Next, the operation for stopping the reduction of power generation asdescribed referring to FIG. 6 will be described.

In FIG. 6, in a case in which the temperature of a predetermined portionassociated with the auxiliary apparatus is relatively high and,simultaneously, the operation period of the power generation apparatus 1is relatively long while the circulation water treatment unit 52 iscontrolled to inhibit boiling in the exhaust heat recovery unit 50,power generation by the power generation apparatus 1 is reduced. Whenthe temperature of the predetermined portion associated with theauxiliary apparatus becomes relatively low by the above operation, theoperation for reducing power generation by the power generationapparatus 1 is stopped.

FIG. 7 is a flowchart illustrating the operation of the power generationapparatus 1 according to the second embodiment.

At the initiation of the operation illustrated in FIG. 7, it is assumedthat the power generation apparatus 1 has already started the operationfor stopping the reduction of power generation described in FIG. 6. Whenthe operation illustrated in FIG. 7 starts, the controller 10 determineswhether the operation status of the air supply unit 34 satisfies afourth predetermined condition (step S41).

Here, in the present embodiment, the fourth predetermined condition maybe determined to be that the current detected by the current sensor 70is below a threshold, e.g., 1.6 A. The threshold is merely illustrativeand may be appropriately set based on the configuration or specificationof each functional unit. In the present embodiment, the fourthpredetermined condition may be determined based on a current detected bythe current sensor 70 when the air blower 96 is reliably operatingwithout a full force.

When the controller 10 determines in step S41 that the operation statusof the air supply unit 34 does not satisfy the fourth predeterminedcondition, the controller 10 returns to step S41 until the fourthpredetermined condition is satisfied. On the other hand, when thecontroller 10 determines in step S41 that the operation status of theair supply unit 34 satisfies the fourth predetermined condition, thecontroller 10 proceeds to step S42.

In step S42, the controller 10 determines whether the temperatureassociated with the power generation apparatus 1 satisfies a fifthpredetermined condition. In step S42, in particular, when thetemperature of a predetermined portion associated with the auxiliaryapparatus in the power generation apparatus 1 is relatively low, thecontroller 10 determines that the fifth predetermined condition issatisfied.

In the present embodiment, for example, when the system temperaturemeasured by the temperature sensor 80 is 42° C. or lower, the controller10 determines that the fifth predetermined condition is satisfied. Here,the temperature is merely illustrative and may be appropriately setbased on the configuration or specification of each functional unit.

When the controller 10 determines in step S42 that the temperatureassociated with the power generation apparatus 1 does not satisfy thefifth predetermined condition, the controller 10 returns to step S41 andperforms the operation of step S41. On the other hand, when thecontroller 10 determines in step S42 that the temperature associatedwith the power generation apparatus 1 satisfies the fifth predeterminedcondition, the controller 10 proceeds to step S43.

In step S43, the controller 10 stops the operation for reducing powergeneration by the power generation apparatus 1. In particular, thecontroller 10 restores the output of power generation by the powergeneration apparatus 1 prior to the operation for reducing powergeneration performed in step S34 of FIG. 6. For example, when theelectric power generated by the power generation apparatus 1 is reducedto 2.5 kW from 3 kW in step S34 of FIG. 6, the controller 10 controlssuch that the power generation apparatus 1 restores the output of 3 kWin step S43 of FIG. 7. As described above, when the temperature of apredetermined portion associated with the auxiliary apparatus becomesrelatively low, the power generation apparatus 1 according to thepresent embodiment can generate electric power at an original outputlevel.

In FIG. 7, when the operation status of the air supply unit 34 satisfiesthe fourth predetermined condition in step S41, whether the temperatureassociated with the power generation apparatus 1 satisfies the fifthpredetermined condition is determined in step S42. However, thedetermination of step S41 and the determination of S42 may be invertedor performed independently of each other.

In the present embodiment, as described above, in a case in which theoperation status of the air supply unit 34 satisfies the fourthpredetermined and, simultaneously, the temperature associated with thepower generation apparatus 1 satisfies the fifth predetermined conditionwhile power generation by the power generation unit (the cell stacks 24)is reduced, the controller 10 may stop the operation for reducing powergeneration by the power generation unit. Here, the fourth predeterminedcondition may be determined to be that power consumption by the airsupply unit 34 is equal to or lower than a predetermined threshold.Alternatively, the fourth predetermined condition may be determined tobe that the current supplied to the air supply unit 34 is equal to orless than a predetermined threshold (e.g., 1.6 A). The fifthpredetermined condition may be determined to be that the temperature ofa predetermined portion of the power generation apparatus 1 is equal toor lower than predetermined temperature (e.g., 43° C.).

By performing the control as described above, when the temperature of apredetermined portion associated with the auxiliary apparatus becomesrelatively low, the power generation apparatus 1 according to thepresent embodiment can generate electric power at an original level.

In the present embodiment, the system temperature measured by thetemperature sensor 80 may be, for example, the internal temperature ofan auxiliary chamber in which the air blower 96 and the circulation pumpincluded in the circulation water treatment unit 52 are accommodated. Inthis case, when the system temperature is equal to or higher thanpredetermined temperature, the controller 10 may perform the operationfor reducing power generation by the power generation apparatus 1. Also,when the system temperature is equal to or lower than predeterminedtemperature, the controller 10 may start operating a heater or the like,for the purpose of antifreezing the power generation apparatus 1.

Although the disclosure has been described based on the figures and theembodiments, it is to be understood that various changes andmodifications may be implemented based on the present disclosure bythose who are ordinarily skilled in the art. Accordingly, such changesand modifications are included in the scope of the disclosure herein.For example, functions and the like included in each functional unit,means, or step may be rearranged without logical inconsistency, so as tocombine a plurality of functional units or steps together or to divide afunctional unit or step. Also, each of the above embodiments does notneed to be practiced strictly following the description thereof but maybe implemented by appropriately combining or partially omitting thefeatures.

For example, the power generation apparatus 1 equipped with the fuelcell has been described in the first embodiment of the above disclosure.However, each of the embodiments of the present disclosure is notlimited to a power generation apparatus equipped with a fuel cell.

For example, the embodiments of the present disclosure may beimplemented by a control apparatus of a fuel cell which does not includethe fuel cell and externally controls the fuel cell. An exampleembodiment of this configuration is illustrated in FIG. 8. A controlapparatus 2 of a fuel cell in this embodiment includes, for example, acontroller 10 and a memory 12, as illustrated in FIG. 8. The controlapparatus 2 controls an external power generation apparatus 1. That is,the control apparatus 2 of the fuel cell according to this embodimentreduces power generation by the cell stacks 24 when an operation statusof the air supply unit 34 satisfies the first predetermined conditionand, simultaneously, temperature associated with the power generationapparatus 1 satisfies the second predetermined condition.

Further, embodiments of the present disclosure may be implemented by,for example, a control program to be performed by the control apparatus2 of the fuel cell as described above. That is, the control program ofthe fuel cell according to this embodiment causes execution of a step ofreducing power generation by the cell stacks 24 when the operationstatus of the air supply unit 34 satisfies the first predetermined and,simultaneously, temperature associated with the power generationapparatus 1 satisfies the second predetermined condition.

REFERENCE SIGNS LIST

1 power generation apparatus

2 control apparatus

10 controller

12 memory

20 fuel cell module

22 reformer

24 cell stack

32 gas supply unit

34 air supply unit

36 reform water supply unit

40 inverter

50 exhaust heat recovery unit

52 circulation water treatment unit

60 hot water storage tank

70 current sensor

80, 84, 86, 88 temperature sensor

96 air blower

98 flowmeter

100 load

200 commercial power grid

1. A power generation apparatus comprising: a power generation unitequipped with a fuel cell; an oxygen-containing gas supply unitconfigured to supply an oxygen-containing gas to the power generationunit; and a controller configured to control power generation by thepower generation unit, wherein the controller reduces power generationby the power generation unit when an operation status of theoxygen-containing gas supply unit satisfies a first predeterminedcondition and a temperature associated with the power generationapparatus satisfies a second predetermined condition.
 2. The powergeneration apparatus according to claim 1, wherein the controller isconfigured to stop reduction of power generation by the power generationunit when a period of reducing power generation by the power generationunit is equal to or longer than a predetermined period and a temperatureassociated with the power generation apparatus satisfies a thirdpredetermined condition.
 3. The power generation apparatus according toclaim 1, wherein the controller is configured to reduce power generationby the power generation unit when the first predetermined condition andthe second predetermined condition are satisfied, and an operationperiod of the power generation apparatus is equal to or longer than apredetermined period.
 4. The power generation apparatus according toclaim 3, wherein the controller is configured to stop reduction of powergeneration by the power generation unit when an operation status of theoxygen-containing gas supply unit satisfies a fourth predeterminedcondition and a temperature associated with the power generationapparatus satisfies a fifth predetermined condition, while powergeneration by the power generation unit is reduced.
 5. The powergeneration apparatus according to claim 1, wherein the firstpredetermined condition is that power consumption by theoxygen-containing gas supply unit is equal to or more than apredetermined threshold.
 6. The power generation apparatus according toclaim 1, wherein the first predetermined condition is that a currentsupplied to the oxygen-containing gas supply unit is equal to or morethan a predetermined threshold.
 7. The power generation apparatusaccording to claim 1, comprising: a heat exchange unit configured tocirculate a heat medium for exchanging heat caused by power generationby the power generation unit, wherein the second predetermined conditionis that a temperature associated with the heat exchange unit is equal toor higher than a predetermined threshold, or that a temperatureassociated with the heat medium is equal to or higher than apredetermined threshold.
 8. The power generation apparatus according toclaim 2, comprising: a heat exchange unit that circulates a heat mediumfor exchanging heat caused by power generation by the power generationunit, wherein the third predetermined condition is that a temperatureassociated with the heat exchange unit is equal to or lower than apredetermined threshold and, simultaneously, a temperature associatedwith the heat medium is equal to or lower than a predeterminedthreshold.
 9. The power generation apparatus according to claim 7,wherein the temperature associated with the heat exchange unit isinternal temperature of the heat exchange unit.
 10. The power generationapparatus according to claim 7, wherein the temperature associated withthe heat exchange unit is a temperature of a predetermined portion of apathway for circulating the heat medium.
 11. The power generationapparatus according to claim 7, wherein the temperature associated withthe heat medium is a temperature of any one of a plurality ofpredetermined portions of a pathway for circulating the heat medium. 12.The power generation apparatus according to claim 8, wherein thetemperature associated with the heat medium is a temperature of any oneof a plurality of predetermined portions of a pathway for circulatingthe heat medium.
 13. The power generation apparatus according to claim3, wherein the second predetermined condition is that a temperature of apredetermined portion of the power generation apparatus is equal to orhigher than a predetermined temperature.
 14. The power generationapparatus according to claim 4, wherein the fourth predeterminedcondition is that power consumption by the oxygen-containing gas supplyunit is equal to or less than a predetermined threshold.
 15. The powergeneration apparatus according to claim 4, wherein the fourthpredetermined condition is that a current supplied to theoxygen-containing gas supply unit is equal to or less than apredetermined threshold.
 16. The power generation apparatus according toclaim 4, wherein the fifth predetermined condition is that a temperatureof a predetermined portion of the power generation apparatus is equal toor lower than a predetermined temperature.
 17. A control apparatus of apower generation apparatus that includes: a power generation unitequipped with a fuel cell; an oxygen-containing gas supply unitconfigured to supply an oxygen-containing gas to the power generationunit; and a controller configured to control power generation by thepower generation unit, wherein the control apparatus reduces powergeneration by the power generation unit when an operation status of theoxygen-containing gas supply unit satisfies a first predeterminedcondition and a temperature associated with the power generationapparatus satisfies a second predetermined condition.
 18. A controlprogram to be performed by a control apparatus of a power generationapparatus that includes: a power generation unit equipped with a fuelcell; an oxygen-containing gas supply unit configured to supply anoxygen-containing gas to the power generation unit; and a controllerconfigured to control power generation by the power generation unit,wherein the control program causes the control apparatus to perform astep of reducing power generation by the power generation unit when anoperation status of the oxygen-containing gas supply unit satisfies afirst predetermined condition and a temperature associated with thepower generation apparatus satisfies a second predetermined condition.